Widely used, for example, in motor vehicle air conditioners in place of conventional serpentine condensers are condensers which comprise, as shown in FIG. 13, a pair of headers 50, 51 arranged in parallel and spaced apart from each other, parallel flat heat exchange tubes 52 made of aluminum and each joined at its opposite ends to the two headers 50, 51, corrugated aluminum fins 53 each disposed in an air flow clearance between the adjacent heat exchange tubes 52 and brazed to the adjacent tubes 52, an inlet pipe 54 connected to the upper end of peripheral wall of the first 50 of the headers, an outlet pipe 55 connected to the lower end of peripheral wall of the second 51 of the headers, a first partition 56 provided inside the first header 50 and positioned above the midportion thereof, and a second partition 57 provided inside the second header 51 and positioned below the midportion thereof, the number of heat exchange tubes 52 between the inlet pipe 54 and the first partition 56, the number of heat exchange tubes 52 between the first partition 56 and the second partition 57 and the number of heat exchange tubes 52 between the second partition 57 and the outlet pipe 55 decreasing from above downward to provide groups of channels. A refrigerant flowing into the inlet pipe 54 in a vapor phase flows zigzag through the channel groups as units within the condenser before flowing out from the outlet pipe 55 in a liquid phase. The condensers of the construction described are called multiflow condensers, and realize high efficiencies, lower pressure losses and supercompactness (see, for example, the publication of JP-A No. 1994-281373).
It is required that the heat exchange tube 52 of the condenser described be excellent in heat exchange efficiency and have pressure resistance against the high-pressure gaseous refrigerant to be introduced thereinto. Moreover, the tube needs to be small in wall thickness and low in height so as to make the condenser compact.
As disclosed in the above publication, the heat exchange tube 52 which is excellent in heat exchange efficiency for use in such condensers comprises two flat walls which are parallel to each other, opposite side walls interconnecting the two flat walls at the respective opposite side edges thereof, and a plurality of reinforcing walls interconnecting the two flat walls, extending longitudinally of the tube and spaced apart from one another as positioned between the opposite side walls, the tube having parallel fluid channels formed inside thereof, each of the reinforcing walls being formed from a ridge projecting inward from one of the flat walls integrally therewith and a ridge projecting inward from the other flat wall integrally therewith by brazing the two ridges to each other as positioned end-to-end.
Such a flat heat exchange tube is fabricated from a metal plate having two first portions 60 for making the flat walls, a second portion 61 interconnecting the first portions 60 for forming one of the side walls, two third portions 62 projecting from the respective first portions 60 integrally therewith each at a side edge thereof opposite to the second portion 61 for making the other side wall, and a plurality of ridges 63 formed on each first portion 60 integrally therewith, arranged at a spacing widthwise thereof and projecting in the same direction as the third portion 62, by bending the metal plate to the shape of a hairpin at the second portion 61 to place the third portions 62, as well as the opposed ridges 63 in each pair, end to end and obtain a heat exchange tube blank P (see FIG. 14), and brazing the third portions 62 of the blank P to each other and the opposed ridges 63 thereof in each pair to each other. To prevent the third portions 62 from separating from each other in the heat exchange tube blank P, a ridge 64 formed in the end face of one of the third portions 62 is forced into a furrow 65 formed in the end face of the other third portion 62 by a press fit. Before the metal plate is bent to form the tube blank P, each ridge 63 on one of the first portions 60 and the corresponding ridge 63 on the other first portion 60 are positioned symmetrically about the widthwise center line of the metal plate.
For example, the publication of JP-A No. 1993-7958 discloses an apparatus for use in temporarily assembling headers, flat heat exchange tube blanks and fins into a unit which is to be brazed to fabricate such a condenser as described above. This apparatus comprises a guide fixedly mounted on a work table and provided in its upper side with a plurality of blank grooves extending laterally of the table and having a width corresponding to the thickness of the tube blanks, and a pair of header supports provided on the work table respectively at the left and right sides of the guide and movable toward or away from each other.
The headers, heat exchange tube blanks and fins are temporarily assembled in the following manner using this apparatus. One end of one of the tube blanks is placed into an insertion hole of one of the headers, and the other end of another one of the tube blanks is placed into an insertion hole of the other header. All the remaining tube blanks are fitted into respective blank grooves of the guide. The headers are then arranged on the respective header supports. The header supports are subsequently moved toward each other, whereby opposite ends of the tube blanks are placed into respective insertion holes of the headers. The headers and the heat exchange tube blanks are thereafter removed from the header supports and the guide, and corrugated fins are arranged between the adjacent tube blanks. In this way, the headers, heat exchange tube blanks and fins are temporarily assembled into a unit.
However when the heat exchange tube blank P shown in FIG. 14 is used as the tube blank, we have found that the following problem is encountered with the conventional temporarily assembling apparatus.
Such heat exchange tube blanks P are produced by cutting an elongated heat exchange tube blank into predetermined lengths while continuously forming the elongated tube blank, so that the cutting force is likely to cause the ridge 64 to slip off from the furrow 65 at the cut end portion, permitting the third portions 62 of the tube blank P to separate from each other and form an opening. This gives the end portion of the tube blank P a thickness T which is greater than the width S of the insertion hole H1 formed in the header H, with the result that the end portion of the tube blank P can not be placed into the insertion hole H1 of the header H.
An object of the present invention is to overcome the above problem and to provide a tube blank correcting member for use in temporarily assembling heat exchangers which makes it possible to reliably insert the corresponding ends of heat exchange tube blanks into respective insertion holes of a header, and a temporarily assembling apparatus and method for heat exchangers.